Optical switch fabrics (OSF) are being considered as a powerful alternative to electrical switch fabrics for the next generation of Terabit/s IP routers. OSFs have been shown to be able to overcome the limitations of fully electrical solutions in throughput capacity and power consumption. However, some recently demonstrated OSFs do not support broadcasting, a desired feature from a networking point of view. In general, broadcasting requires wavelength multiplexing of the data channels on the transmitter side and distribution of the WDM signal to every receiver. In this manner, each receiver may select any channel on demand.
Tight specifications concerning response time, selectivity, and wavelength accuracy are required for an OSF to be used in receivers for such channel selection. Recent progress in the development of rapidly tunable lasers suggests investigating coherent detection schemes for the filtering process. Tunability of the local oscillator (LO) wavelength would allow for selection of any channel out of the WDM data signal as long as it resides in the tuning range of the laser. Additional advantages of this approach would be an amplification of the data signal through the relatively high power of the LO and an ultra-short channel access time since such WDM lasers are substantially the fastest tunable wavelength-heterodyne components known today. However, while the wavelength accuracy of WDM lasers is in the 10 to 100 pm wavelength range, a frequency mismatch between a modulated optical data signal and a WDM laser when used as a LO make it necessary to have some kind of slow and time consuming wavelength fine tuning in conventional coherent detection schemes.